Interpret the equation y = mx + b as defining a linear function, whose graph is a straight line; give examples of functions that are not linear. For example, the function A = s<sup>2</sup> giving the area of a square as a function of its side length is not linear because its graph contains the points (1,1), (2,4) and (3,9), which are not on a straight line.

Warm-up

10 minutes

Each day, students complete a Warmup that usually consists of spiraling the previous day's material, in addition to older material. Warm-up problems also sometimes extend lessons that students have encountered before to more unfamiliar contexts.

For a video narrative about how I structure each lesson, and how the warm-up fits in, click here.

In this case, the warm-up not only gets kids to practice finding slope, it pushes conceptual understanding of horizontal lines. I push the idea of "NO ROBOTS" - meaning that they can solve #2 without having to robotically apply the formula. What should be the slope of a horizontal line?